Conventionally, there is well known a press molding device for drawing process having a die, a punch and a cushion ring that a work piece is pressed to the punch facing the die while the work piece is pinched by the die and the cushion ring so as to perform molding process. For instance, an example of the device is described in the Japanese Patent Laid Open Gazette 2002-86219.
Such a press molding device may have plural cushion rings. For example, a press molding device shown in FIG. 11 comprises a die 102 which is an upper mold, a punch 103 facing the die 102, a lower mold 104 constructed integrally with the punch 103, a first cushion ring 105 which is a ring-shaped member arranged around the punch 103, and a second cushion ring 106 arranged at the inner peripheral side of the first cushion ring 105.
Then, at the time that the die 102 is moved downward so as to perform molding, a work piece W interposed between the die 102 and the punch 103 is pinched by a pressure surface 102a of the die 102, a pressure surface 105a of the first cushion ring 105 and a pressure surface 106a of the second cushion ring 106 so as to prevent crease and crack of the work piece W.
At the time of molding by the above-mentioned press molding device, the die 102 is moved downward and the work piece W is pinched by the pressure surface 102a of the die 102, the pressure surface 105a of the first cushion ring 105 and the pressure surface 106a of the second cushion ring 106, and then the die 102 is moved downward further so that the work piece W is pressed to the punch 103 and is deformed, whereby the work piece W is processed to be molded. The work piece W is pinched completely by the punch 103 and the die 102 so as to finish the processing.
In the case that the work piece W is pressed to the punch 103 to be molded, the contact area between the inner second cushion ring 106 and the other members is small so that the posture of the second cushion ring 106 is unstable. Then, the regular posture may not be maintained and disorder may occur, thereby causing slant or the like. When the second cushion ring 106 is slanted, abnormal abrasion of the punch 103 and the die 102 and defects of the work piece W after processed such as crease and crack are liable to occur.